1. Field of the Invention
This present invention is directed to top drive drilling systems, joint breaker/making apparatus for use with such systems; and methods of their use.
2. Description of Related Art
In several prior art drilling systems, a continuous fluid circulation system is used so that tubulars added to a string, e.g. but not limited to drill pipe added to a drill string, are added without terminating the circulation of fluid through the string and in the wellbore. Typical continuous circulation systems permit the making or breaking of a threaded connection between two tubulars, e.g. a saver-sub-drill-pipe connection in a top drive drilling system, within an enclosed chamber. The saver-sub-drill-pipe connection is broken with part of the saver sub located within a pressure chamber of the continuous circulation system so that drilling fluid is continuously circulated through the string and wellbore. Certain prior art wellbore drilling operations involve the addition of drill pipes to a drill string that extends down into a wellbore and which is rotated and urged downwardly to drill the wellbore. Typically drilling fluid is circulated through the drill string and back up an annular region formed by the drill string and the surrounding formation to lubricate and cool the bit, and to remove cuttings and debris from the wellbore. In one prior art method a kelly bar, connected to a top joint of the drill string, is used to rotate the drill string. A rotary table at the derrick floor level rotates the kelly bar while simultaneously the kelly bar can move vertically through a drive bushing within the rotary table at the rig floor. In another prior art method, top drive drilling unit suspended in a derrick grips and rotates the drill string and a kelly bar is not used.
As more pieces of hollow tubular drill pipe are added to the top of a drill string, drilling is halted and successive pieces of drill pipe are connected to the drill string. To remove drill pipe from the string, to “trip out” of a hole, (e.g. to replace a drill bit or to cement a section of casing), the process is reversed, again requiring cessation of drilling operations which can entail stopping circulation of drilling fluid until operations re-commence. Re-instituting the flow of drilling fluid and reconstituting the required column of it in the wellbore can take a significant amount of time and the effects of removing and then reintroducing the drilling fluid into the wellbore can have harmful effects on both equipment and on the wellbore and to the formation being drilled through. In such circumstances, expensive and time-consuming of additional fluid weighting may be required
It is often preferable to maintain drilled cuttings in suspension in the drilling fluid to facilitate moving them away from a drill bit and to prevent them from falling back down in a wellbore. Cessation of fluid circulation can cause the drilled cuttings to sink. To counter this in many prior art systems additional fluid weighting is attempted, often increasing the viscosity of the fluid. This results in the need for more pumping power at the surface to move the thicker fluid; but such an increase in pump force can result in over pressuring of a downhole which can cause formation damage or loss of fluids downhole.
Certain prior art continuous circulation systems are proposed in U.S. Pat. No. 6,412,554 which attempt continuous fluid circulation during the drilling operation, but in these systems rotation of the drill string is stopped and re-started in order to make and break tubular connections. This involves significant loss of drilling time. Also, starting rotation of the drill string can result in damaging over torque portions of the drill string.
U.S. Pat. No. 6,315,051 discloses continuous drilling/circulation systems and methods; but with these systems drilling is halted during tubular connection procedures.
U.S. Published patent application No. 0030221519 published Dec. 4, 2003 (U.S. Ser. No. 382,080, filed: Mar. 5, 2003) discloses an apparatus that permits sections of tubulars to be connected to or disconnected from a string of pipe during a drilling operation. The apparatus further permits the sections of drill pipe to be rotated and to be axially translated during the connection or disconnection process. The apparatus further allows for the continuous circulation of fluid to and through the tubular string during the makeup or breakout process. The apparatus defines a rig assembly comprising a top drive mechanism, a rotary drive mechanism, and a fluid circulating device. Rotation and axial movement of the tubular string is alternately provided by the top drive and the rotary drive. Additionally, continuous fluid flow into the tubular string is provided through the circulation device and alternately through the tubular section once a connection is made between an upper tubular connected to the top drive mechanism and the tubular string. This application also discloses a method for connecting an upper tubular to a top tubular of a tubular string while continuously drilling, the method including steps of: operating a rotary drive to provide rotational and axial movement of the tubular string in the wellbore; positioning the upper tubular above the top tubular of the tubular string, the upper tubular configured to have a bottom threaded end that connects to a top threaded end of the top tubular; changing a relative speed between the upper tubular and the top tubular to threadedly mate the bottom threaded end of the upper tubular and the top threaded end of the top tubular such that the upper tubular becomes a part of the tubular string; releasing the tubular string from engagement with the rotary drive; and operating a top drive to provide rotational and axial movement of the tubular string in the wellbore.
In some prior art systems in which a top drive system is used for drilling, a stand of drill pipe (e.g. a 90 foot stand with three interconnected pieces of drill pipe) is threadedly connected to and below a saver sub. Once drilling has proceeded down to the extent of the length of a stand, the saver sub is located within a pressure chamber of a continuous fluid circulation system. In order to add a new stand with this type of prior art system, the connection with the saver sub is broken by the continuous fluid circulation system. The top drive drilling unit is raised and, along with it, the saver sub is raised and exits from the top of the continuous circulation system. In order, then, to connect a new stand of drill pipe, the top drive drilling unit's elevator is moved away from the drill string's center line. An elevator is associated with the top drive drilling unit, but typically this elevator is not used to receive and support the new stand because is cannot stab the saver sub into the stand and release it and, often, the saver sub is so long that longer support links would be needed. Also, in many cases, as a top drive drilling unit is raised, it is desirable to backream the wellbore as the top drive drilling unit is raised. In a backreaming operation the rotation of the drill string is not reversed. If a top drive drilling unit is used, it is not possible to determine or control which two pieces of drill pipe in the drill string will be disconnected, but, in adding a new stand, it is the saver-sub-drill-pipe connection which must be broken.